package com.wc.AlgoOJ_homework.AlOJ模块测试I.H_数组切分;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/5/12 11:26
 * @description http://43.138.190.70:8888/p/537?tid=663e1b10d39d10926ed3f7fa
 */
public class Main {
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 10010, P = (int) 1e9 + 7;
    static int[] a = new int[N];
    // f[i] 表示前i个数满足的方案数
    static int[] f = new int[N];
    static int n;

    public static void main(String[] args) {
        n = sc.nextInt();
        for (int i = 1; i <= n; i++) a[i] = sc.nextInt();
        f[0] = 1;
        for (int i = 1; i <= n; i++) {
            int minV = a[i], maxV = a[i];
            for (int j = i; j >= 1; j--) {
                minV = Math.min(minV, a[j]);
                maxV = Math.max(maxV, a[j]);
                if (i - j == maxV - minV) {
                    f[i] = (f[i] + f[j - 1]) % P;
                }
            }
        }
        out.println(f[n]);
        out.flush();
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}
